It sames that RecycleView in Fragment FrameLayout can not be recognized

[Starved Midnight]

I create a RecycleView in FrameLayout which belong one Fragment
but it sames that android can not recognize it.
I tried binding.view_id and use findviewbyid, those functions all no use.
android studio has no error, but do not display view.

this is my layout.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android">
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ui.rec.RecFragment">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/rec_view"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:scrollIndicators="bottom"
        android:fadeScrollbars="false"
        android:layout_gravity="center_vertical"
        android:focusable="true"
        android:focusableInTouchMode="true"
        android:clickable="true"
        android:scrollbarAlwaysDrawHorizontalTrack="true"
        android:scrollbars="none"
        app:layoutManager="LinearLayoutManager"/>

</FrameLayout>

and this is my fragment.kt

package com.ml.test.ui.rec

import android.R
import android.os.Bundle
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.lifecycle.ViewModelProvider
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.ml.test.databinding.FragmentTopBinding
import com.ml.test.utils.FaceAdapter
import com.ml.test.utils.NewFace


class RecFragment : Fragment(){
    private lateinit var recViewModel: RecViewModel
    private var _binding: FragmentTopBinding? = null

    private lateinit var recyclerView: RecyclerView
    private lateinit var newsArrays:ArrayList<NewFace>

    lateinit var imageId:Array<String>
    lateinit var heading:Array<String>

    // This property is only valid between onCreateView and
    // onDestroyView.
    private val binding get() = _binding!!

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        recViewModel =
            ViewModelProvider(this).get(RecViewModel::class.java)

        _binding = FragmentTopBinding.inflate(inflater, container, false)
        val root: View = binding.root
        try{
            // val rootView: View = inflater.inflate(com.ml.test.R.layout.fragment_rec, container, false) // not work
            // recyclerView = rootView.findViewById(com.ml.test.R.id.rec_view)  // not work
            // recyclerView = root.findViewById(com.ml.test.R.id.rec_view)  // not work
            recyclerView = root.recView // not work
            Log.d("rec_frag", "find Recycle View")
        }catch (e: Exception){
            Log.i("rec_flag", e.message.toString())
        }
        dataInitialize()
        if(::recyclerView.isInitialized) {
            // recyclerView.layoutManager = LinearLayoutManager(activity)
            var faceAdapter = FaceAdapter(newsArrays)
            faceAdapter.notifyDataSetChanged()
            recyclerView.adapter = faceAdapter
            recyclerView.setHasFixedSize(true)
            Log.d("rec_frag", "Recycle View init data")
        }

        return root
    }

    override fun onDestroyView() {
        super.onDestroyView()
        _binding = null
    }

    private fun dataInitialize(){
        newsArrays = arrayListOf()

        imageId = arrayOf(
            "https://i.imgur.com/DvpvklR.png",
            "https://i.imgur.com/DvpvklR.png"
        )

        heading = arrayOf(
            "test1",
            "test2"
        )

        for (i in imageId.indices){
            val news = NewFace(imageId[i], heading[i])
            newsArrays.add(news)
        }

    }

}

and debug out put: findViewById can not be null

[Starved Midnight]

I fig it out, because I use wrong Fragment Binding class

I must use

import com.ml.test.databinding.FragmentRecBinding

not

import com.ml.test.databinding.FragmentTopBinding

and this class is auto generate by Framework, and if u copy code, it has no error even use wrong class.

by the way, why user must care those class?